Composition for a pencil lead



Patented Sept. 4, 1951 2,566,754 COMPOSITION FOR A PENCIL LEAD CharlesH. Van Dusen, Jr., Willoughby, Ohio and Oscar E. Weissenborn, Verona, N.J., assignors to Addressograph-Multigraph Corporation, Wilmington, Del.,a corporation of Delaware No Drawing. Application September 9, 1948,Serial No. 48,534

This invention relates to a planographic imageforming pencil and to aso-called lead or writing rod therefor for use in forming planographicimages upon master planographic printing plates including aluminum andpaper or like cellulose base master planographic printing plates.

A number of problems are encountered in the manufacture of planographicimage-forming writing rods or so-called leads and pencils embodying thesame which are peculiar to such planographic image-forming pencils andwhich are not encountered in the manufacture of common so-called leadpencils. Among these problems are: A planographic image-forming pencilmust be capable of forming an inscription or image which will produce asatisfactory number of copies from the master plate upon which 1 Claim.(Cl. 106-19),

the image is written; it must be capable of making uniform lines, thatis to say, lines which are of substantially uniform width throughouttheir entire length upon the master plate; the writing instrument, thatis to say, the substantially cylindrical writing rod or so-called leadwhich is embodied in such a planographic pencil must be neither too softso that the inscription or image formed thereby will wash off the platereadily or so that it will produce lines Which will vary in width as thepencil moves across a master aluminum or paper or like planographicplate on which it is being used to write an image, and it must not besufliciently hard to scratch such a master planographic printing plate;and it must have good ink-respective and ink-retentive properties sothat it will be receptive to and will retain the lithographic inks usedin making reproductions from the master plate.

Accordingly, an object of the present invention isto provide a new andimproved imageforming planographic pencil embodying a writing instrumentor so-called lead which has good image-forming properties and which willproduce images having good ink-receptive and inkretentive properties forplanographic or lithographic inks; which is sufficiently hard to enableit to make lines of uniform width upon a paper or other planographicprinting plate and to prevent the image made thereby from washing offthe plate; and which is otherwise a satisfactory image-formingplanographic pencil.

Another object of the invention is to provide a novel composition formaking the substantially cylindrical writing rods or so-called leads ofthe new planographic pencil.

A further object of the invention is to provide a a new and improvedplanographic image-forming lead or writing instrument for use in aplanographic image-forming pencil which may be employed in aplanographic image-forming pencil 2 of any suitable character includingthose of the mechanically propelled type.

Other and further objects of the present invention will be apparent fromthe following description and claims which describe preferredembodiments of the invention and the principles thereof and what we nowconsider to be the best mode in which we have contemplated applyingthose principles. Other embodiments of the invention embodying the sameor equivalent principles may be used and changes may be made as desiredby those skilled in the art without departing from the present inventionand the purview of the appended claims.

A typical formula which may be employed in preparing the so-called leador the substantially cylindrical writing rod or writing instrument whichmay be embodied in a planographic imageforming-pencil, in the practiceof the present invention, may be that which is shown in the followingexample:

v Example No. 1 Parts by weight Nigrosine 35 Japan-wax 2 Aluminumstearate 40 Methyl cellulose solution( one part dissolved in six partsof water, by weight) 27.6

In the manufacture of the new planog raphic image-forming pencil, andthe new planographic image-forming lead or writing rod therefor, thenigrosine and aluminum stearate referred to in the foregoing Example No.1 may be mixed together in the dry state and the methyl cellulose may bedissolved in approximately six times its weight of Water, whereupon thenigrosine-aluminum stearate mixture and the aqueous methyl cellulosebinder solution may be thoroughly mixed for a period of two or threehours, in a suitable mixer. The Japan wax may then be melted to liquidform and added to the aforesaid mixture of nigrosine, aluminum stearateand methyl cellulose binder and the resulting mixture further thoroughlymixed for a period of two hours. The resulting base mixture is of doughyconsistency and may be rolled and extruded in the form of substantiallycylindrical rods and out to suitable lengths to form the newplanographic image-forming leads or substantially cylindricalplanographic image-forming writing rods and the new planographicimage-forming pencils embodying the same, whereupon the said leads orrods may then be forced dried until their moisture content isapproximately three (3) per cent, by weight.

The thus prepared planographic image-forming leads or substantiallycylindrical rods may then be encased or enclosed in grooved woodenformed in one of two complementary SBCtiOIIS'Of. a wood or like pencilcasing, adhesively securing the two complementary halves or sections ofthe pencil casing together with. the substantiallycylindrical writingrod or so -called lead therebetween; suitably shaping the.outer-surfaceof.

the pencilcasing as by forminghexagonalfaces thereon; and then suitablyfinishing the pencil casing as by sanding and painting the. same.

In addition to being encased in a grooved wooden casing the newplanographic imageforming leads'or writing rods may, if desired; beemployed in pencils of .the mechanical type.

- It will thus be seen that the new planographlc image-forming writingrods or: so-calledleads which are prepared according. to the foregoingExample No. l, are'comprised-of; the. dried. reaction productof anintimate mixture'ofi an 7 aqueous solution of a binder, namely,a'so'lution oisi methyl cellulose in water, and. the; balance a mixture.of the solidmaterials referred'to' in the foregoing Example. No. 1.namely,., nigrosinej. Japanjwax' and; aluminum stearate..-

.In'; placev of the Japan specified in the foregoing Example-No. 1 we.may: employ suitable equivalent quantities'of one of the following substances or mixtures thereof, namely, tallow, stearici-acid, carnaubawax, bee's wax; paraffin wax; and spermaceti.

The aqueous solution of methyl cellulose (binder) specified in theforegoing Example No. lma'y be employed... within a. rather wide rangeoflfrom approximately 10 per cent to'approximately per cent, by weight,of. the complete pencil base mixture. However, it has been found that:the. resulting planographic image-forming pencil. or. writing rodbecomes tooweak 'if: the percentage of theaqueous.methyl-cellulosebinder is r'educed below the minimum of lo 'pencent', as:

specified; whereas if? the percentage of the aqueous'methyl. cellulosebinder is increased'substantially. in excess of the maximum of 50 percent specified the writing or. planographicv imageforming qualities ofthe. resulting pencil or writ-- ingrod are unsatisfactory.

, In place oftheaqueous solution'of methyl cellulosespecified intheforegoing Example No.1. suitable equivalent quantities of thefollowing;

materials, or. mixtures thereof, maybe employed as-the. binder, namely,ethyl cellulose, carboxy methyl cellulose,. gum tragacanth, polyvinyla1- cohol and clay. v

Indulin' may be employed in place. of the, nigrosine.specified in theforegoing, Example No. land in'place of. the aluminum stearate specifiedwe also employv suitable equivalent quantities of calcium stearate orzinc stearate, or mixturesof these materials.

Another composition which may be employed 7 in. preparing the base forthe new substantially cylindrical planographic image-forming pencils or:writing rods is illustrated in the following example in which all partsindicated are by weight:

Example No. 2

Methyl cellulose solution (one part dissolved in six parts of water, byweight) 27.6;

tics of vthe present invention.

creased as much asten per cent of the quantities specified while stillaifording a planographic image-forming lead or writing rod having thenovel and desirable properties and characteris- The Japan wax, or othermaterial substituted therefor, embodied in the substantiallycylindricalplanographic image-forming Writing rod or instrument ?for thenew planographic imageforming pencil enables a planographic imageformingpencil embodying the new planographic image-forming pencil or writingrod to slide or move easily over the surface of a planographic printingplate during the writing or image-formingoperation; the nigrosine- (orindulinsubstituted therefor) is an image-forming material and. impartsnecessary color to the substantially cylindrical. planographicimage-forming writing; rod or'instrum-ent, namely, a black'color;thBfi-lll: minumstearate, or-v other material substituted therefor, isalso an image forming material; and thesmethyl cellulose, with orwithout clayiserves as. a binder to bind the various ingredients to;-gether.

' It has been found that the new planographie image-forming so-calledleads or writing rods prepared according to the present invention'have'good image-forming properties, and thatiim ages formed thereby have'goodink receptive proper ties for lithographic inks; that they aresufficient-v ly-hard to enable it to form goodimagesgincluda ing linesof. uniform width, on paper and like. planographic. printing plates;that they. provide. images which will. not readily wash on such.

plates; and that they provide imageswhichzwilh and that the inventionhas. the desirable. ad-- rod material consisting essentially of thedried-r product of. an intimate mixture of the: following: materialswithin the range of the'quantities specified; all parts being by weight:

Nigrosine 31.5 to, 38.5.- Japanwax 1.8 to 22- Aluminum stearate 36. to44' Methyl cellulose (one part dissolved in six parts of water, byweight) 24.84; to 301361 CHARLES H. VAN DUSEN, JR. OSCAR, E.WEISSENBORN.

(References l on. following page REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 7,907 Walpuski Oct. 9, 1877376,456 Walpuski Jan. 17, 1888 1,937,105 Thomsen Nov. 28, 1933 Number 5Number

